Scratchers for well bores



, Aug. 13, 1957` J. R. BAKER v scRATcHERs FOR WELL BoPEs Filed 24. 1954 INVENTORQ JOU/N R. BAKEQ,

BY Y Y United States Patent O SCRATCHERS FOR WELL BGRES John R. Baker, Pasadena, Calif., assignor to Baker @il '[`00l s, Inc., Los Angeles, Calif., a corporation of (latiorma Application May 24, 1954, Serial No. 431,654

17 Claims. (Cl. 16d-173) The present invention relates to subsurface well tools, and more particularly to devices for scratching or scraping the walls of open well bores, conduits of Various kinds disposed in well bores, and the like.

An object of the present invention is to provide a wall scratcher embodying spring fingers that `can collapse more fully toward the casing string on which the scratcher is mounted during lowering of the casing string in the well bore, to preclude any substantial 'scratching of the fingers against the wall of the well bore during such lowering movement. The spring fingers, however, are effective to engage and scratch the wall of the well bore with eifective force during upward movement of the well casing therewithin.

Another object of the invention is to provide a wall scratcher of simple and rugged construction, which is easy to a'ssemble and more economical to produce.

A further object of the invention is to provide a hinge type of wall scratcher which can be placed laterally around -a well casing section, and in which the hinges can be made of stronger and sturdier construction without increasing the over-all outside diameter of the wall scratcher. i

Yet another object ofthe invention is to provide a wall scratcher including outwardly directed spring lingers, to engage the wall of the well bore, mounted on a supporting member, iu which the spring fingers do not interfere with each other at the supporting member, insuring the ap- `propriate flexing action of the ingers during the Wall It will now 'be described in detail, for the purpose of il- 2 lustrating the general principles of the invention; but it is to be understood that such detailed description is not to be taken in a limiting sense, since the scope of the invention is best defined by the appended claims.

Referring to the drawings:

Figure l is a side elevation of a Wall scratcher mounted on a casing section, with portions disclosed in longitudinal section; p

p Fig. 2 is a cross-section taken along the line 2-2 on Fig. l;

Fig. 3 is an enlarged fragmentary longitudinal section taken along the line 3--3 on Fig. 2;

Fig. 4 is an enlarged fragmentary section disclosing the manner yof mounting a scratcher element on its associated supporting member;

Fig. 5 is an enlarged fragmentary cross-section `of a single spring element and its associated supporting sleeve.

The wall scratcher A disclosed in the drawings is designed to be mounted upon a casing string `section B for the purpose of removing the mud cake C -or other material that may be coating the inner wall of a well bore D in which the casing string is to bedisposed. Scratchers r"ice are ordinarily used to remove the mud cake or 'sheath from a particular portion of the well bore, for the pulpose of insuring a good bond between the formation wall Iand cement "slurry, or the like, pumped down the casing string for upward passage through the annulus around the latter. It is preferred not to disturb the mud cake C in the well bore to any substantial extent, eircape along the portions of the formation wall at which the cement slurry is to be deposited. For that reason, the wall scratcherv A is designed to provide very little, if any, engaging force against the mud cake during lowering of the casing string in the well bore. But upon elevating of the casing string B and scratcher A in the well bore, the scratcher should have maximum effectiveness in operating upon the wall of the well bore D.

The scratcher A is mounted on the casing section B, there preferably being relative longitudinal movement to a limi-ted extent allowed between the two devices. The wall scratcher includes a supporting sleeve structure 10 slidable on the casing section B. This sleeve structure is adapted to engage stop elements 11, 12, in the form of ring members, suitably secured, as by welding, to the casing section on opposite sides of the scratcher, the stop members 11, 12 being disposed several feet apart, or a much greater distance than the vertical length of the sleeve structure, in order to permit a limited amount of relative longitudinal movement between the `casing section and the scratcher, During downward movement of the casing string B in the well bore D, the upper stop ring 1]. engages the sleeve structure 10, forcing the scratcher A downwardly through the well bore. Slight upward movement of the casing string, such as occurs in lifting it out of the rotary table slips (not shown) at the top of the well bore, will not move the scratcher device in an upward direction since the lower stop element 12 will not have been moved .upwardly suliciently to engage the lower end of the sleeve structure 10. A greater extent of `upward movement of the casing section will bring the lower ring 12 into engagement with the sleeve structure 10, and cause it to shift the entire scratcher device A upwardly with the casing string B within the well bore D.

The sleeve structure 10 of the scratcher device includes an inner sleeve 13 and an Outer sleeve 14, which may be of the same longitudinal extent as the inner sleeve 13 and suitably spot welded or otherwise secured thereto. The inner sleeve 13 may be made of substantial thickness, so as to withstand relatively great strains, whereas the outer sleeve Mpmay be `made of somewhat thinner gauge material. The inner sleeve 13 is generally cylindrical in form. The outer sleeve 14 is also cylindrical in form, but is provided with one or more outwardly directed bead portions 15. Where more than one bead portion is provided, such bead portions 15 are longitudinally 'spaced from Vone another, each of the beads having a set of circumferentially spaced apertures 16 therethrough, the apertures in one bead preferably being staggered or disaligned with respect to the apertures of the other bead 15.

Each aperture 16 may be bounded 'by sides 17 that are substantially parallel to each otherthe upper end 18 of each aperture terminating at the juncture of the bead 15 with the cylindrical portion of the outer sleeve 1d, whereas the lower side or base 19 of the aperture or opening terminates at the central `or mid-portion 20 of the bead, and preferably above the central plane 21 of the bead normal to the -aXis of the structure 10. Thus, the apertures 16 of each bead are provided in the upper portion of the bead 15, the lower portion of each bead being imperforate. The reasons for'locating the apertures 16 in the upper portion of the bead will be described hereinbelow.

A plurality of spring wirefelements 22 are carried by the sleeve structure 10. The spring wireelements and their cooperation with the sleeve structure are the same at each bead portion of the latter, so that a descrip'- tion of one set of spring elements 22 and one bead 15 -will suliice for both. As specifically disclosed in the drawings, the apertures 16 are substantially uniformly spaced from each other. Disposed within the bead are the base portions 23 of the spring elements, each element consisting of a piece of spring-like steel wire having its central base portion disposed within the bead 15. This base portion 23 merges at its opposite ends into a pair of spring lingers 24 extending outwardly through apertures 16 in the bead. Thus, a spring iinger 24 of a spring .element 22 will extend out through one aperture 16 of the bead 15, the base portion 23 being disposed within the beadV y and running to the next adjacent bead aperture 16, where` it is connected to `or merges into the other finger 24, of the spring element, this latter finger extending through such adjacent aperture.

Individual spring elements 22 will lne-Carried by the sleeve structure 10, the base v23 of each of these spring elements being Vdisposed within the bead 15, the -spring iingers 24 extending outwardly through bead apertures 16 on opposite sides of the basetportion 23. From the drawings, and particularly Fig. 2, it is apparent that the fingers 24 of adjoining spring elements 22 will extend outwardly through the saine bead aperture 16, the sides 17 of each aperture being spaced suliiciently apart to provide an aperture width that is greater than twice the diameter of a spring wire, to `permit the spring wire elements 22 to move without interference from each other.

The springngers 24 are of substantial lengthand will extend laterally outward with their outer ends 25 engageable with the wall of the well bore, in order that the fingers will perform a scratching action on the wallduring upward movement of the well casing B and scratcher A in the well bore D. During downward movement of the casing string and the scratcher device in the well bore, the spring elements 22 may fold upwardly, to avoid the imposition of any spring force on the wall of the well bore. The ability of the spring elements 22 to function in the manner described will be apparent from an inspection of the scratcher device, particularly as shown in Figs. 3 and 4. As shown most clearly in Fig. 4, the diameter of the wire from which the spring scratcher element 22 is made is much smaller than both the vertical and horizontal distances across the inner groove portion 26V of the bead 15. That is to say, the greatest lateral distance from the periphery of the inner sleeve 13 to the outermost portion of the bead wall is much greater (two to three times greater) than the diameter of they spring wire from which the scratcher element 22 is made. This is also true of the vertical distance between the opposed inner side walls 27 of the bead 15. Thus, the base portions 23 of each spring element 22 can move to a substantial extent vertically within and with respect to the bead 15, as well as laterally within and with respect to the bead. The spring elements 22 may be folded upwardly in the manner shown in broken lines in Figs. 3 and 4', to lie closely adjacent the sleeve structure 1i), which will insure the lack of any substantial contact, or of no contact whatever, between the spring iinge'rs 24 andthe wall of the well bore D. The ability of the spring elements 22 to fold upwardly against the sleeve structure 10 is permitted since the base portion 23 of each element can move within the .bead groove, 26 downwardly into engagement with its lower sidewall 27, which will allow the ngers 24 to swing inwardly against the periphery of the outer sleeve 14. The fact that the upperend 18 of each aperture 16 lies at the juncture between the bead and the upper cylindrical portion of the sleeve 14 permits the spring elements 22 to fold against the sleeve 14 to a position substantially-parallel relation-to the Vaxis of the apparatus.V With respect to the lower set of spring elements 22, 'their ability -to'fold inwardly is limited byA their engagement with the upper bead 15, `as clearly indicated in Fig. 3. However, such lower set of spring elements will still be completely removed from engagement with the wall ofthe well bore D.

The spring elements 22 can swing in adownward direction to place their spring fingers 24 in scratching engagement with the wall of the well bore D. As will be clear from Fig. 4, the downward swinging of each spring element brings each spring finger 24V into .engagement with the lower or base side of an aperture 16, the

e base 23 of each spring element being shifted upwardly intoI engagement with the upper side 27'oi`V the bead groove 26 and also against the periphery of theinner sleeve 13. Accordingly, when the spring element 22 is swung downwardly to the full line position shown in Fig. 4, the lower i side 20 of each aperture acts as. a fulcrum point about which each spring element will bend or ex, the inner surface 27 of the bead groove 26 and the outer surface of the sleeve 13 preventing upward movement of the spring element base 23. Such, position of the `spring elements 22 will be produced during upward movement of the casing B and sleeve structure 10. During such upward movement, the spring elements 22 .can pivot or swing in a downward direction, whereupon continued upward movement of the casing string and sleeve structure will cause the outer ends of the springs to engage the Wall of the well bore D and cause the spring elements to flex about their points of engagement with the lower sides 20 of the apertures 16, the spring` ngers 24, in effect, tiexing ina downward direction, -as disclosed in broken lines in Fig. 3, and, exerting an outward scratching force upon the wall of the well bore D during the elevating movement of the casing string B and the entire scratcher device A. y

In order to increase the spring force that can be exerted by the scratcher elements 22 against the wall of the well bore D, the spring lingers 24 are caused to overlap one another, to support each other. In addition, the spring fingers 24 of the scratcher elements are so related to each other as to avoid interference with one another at the bead during their swinging movement within the bead 15. To accomplish these purposes, the lingers 24 of each element consist of inner portions 30 which taper or converge toward each other in a direction outwardly of the bead 15, these inner portionsv (which are of relatively short length) merging into outer portions 31 that diverge from each other in a direction outwardly of the bead. The fact of convergence of the inner portions insures that the inner portion of one spring element will not interfere with the inner portion of Aan adjacent spring element extending through the same aperture 16. The inner portion 30 of adjacent elements 22 diverge from each other, as is evident from Fig. 2. Y

The divergence ofthe outer divergent portions 31 of the fingers of each element 22 .causes one outer nger portion-to cross the outer linger portion 31 of an adjacent spring element, the crossing location being at a substantial distance .outwardl from the bead 15. Accordingly, the downward swinging of one" spring nger 24 will cause it to engage-the outer spring portion 31 of anadjoining spring element 22 at :the crossing location 35, so that the spring fingers 24 mutually support one anotherV and result in the transmission of the spring force from finger to finger aroundV the entire circumference of the apparatus. ,It is also to be noted'that the convergence ofthe inner finger portions 30 ofiV each element 22 Vresults in the crossing of the outer inger portions 31 of adjacent elements at a greater distance from the bead 15 than would occur -ifthe inner portions. 30 were made parallel; It is evident that the convergence of the inner spring tinger portions30-toward each other'provides several purposes. Not only does ,it locate the crossing of the outer spring portions 31' at a greater distance from the Vbead 15,. but it also avoids interference in the swinging movement between adjacent spring elements 22, particularly at the common aperture 16 through which thei-r adjacent spring finger portions 30 extend.

It is to be noted that each spring element 22 is comparatively simple, consisting of a spring wire of the proper size that can be bent into the shape disclosed. It is a simple matter to assemble the spring elements 22 in the outer sleeve. All that need be done is to bend the ngers 24 of each element toward each other and slip the ends 25 of the fingers through the apertures 16. When the base portion 23 is disposed within the bead 15, the spring fingers can be released, allowing them to assume their initial shape, with the inner finger portions converging toward each other and the outer finger portions 31 diverging from each other. The convergence of the inner finger portions 30 causes them to embrace the adjacent sides 17 of the two apertures 16 through which such portions extend, precluding inadvertent inward movement of the spring element 22.

All of the spring elements 22 are assembled in the manner described, which will place the outer finger portions 31 in overlapping relation with respect to each other, whereupon the inner sleeve 13 is slipped within the outer sleeve 14 and is spot welded or otherwise secured thereto. The inner sleeve 13 will then positively prevent inward displacement of the base portions 23 of the spring elements from the interior of the bead 15.

The scratcher device A is then mounted on a casing section B and the stop rings 11, 12 disposed on opposite sides of the scratcher device, the latter being welded or otherwise suitably secured to the casing string. The required number of scratchers A is mounted on the casing string at the desired intervals and the casing string is lowered through the well bore D. During downward movement in the well bore, the scratcher elements 22 will swing to an upward and ineffective position, imposing substantially no scratching force upon the wall of the well bore. However, once the casing string B has been run in the well bore to the desired location, the casing can be elevated the required distance, for example, thirty feet, the upward movement causing the lower stop ring 12 for each scratcher to engage the sleeve structure 10, moving the scratcher A in an upward direction and causing the spring elements 22 to engage the wall of the well bore D, the fingers 24 flexing about-the points of contact of the inner finger portions 30 with the bead 15 defining the lower sides 20 of the apertures 16, the fingers 24 bending in a downward direction, such `as disclosed in Fig. 3, to exert an effective scratching force upon the mud cake C, or other coating, on the wall of the well bore D, removing the latter and allowing it to be fiushed to the top of the hole for suitable disposition.

After the casing string B has been reciprocated the required number of times to secure the substantially complete removal of the mud cake C from the wall of the well bore in the region where the scratcher elements A are located, a proper charge of cement slurry can be of the sleeve structure 13. Thus, with the hinge pins 41 removed, or at least withone of the hinge pins removed, the sleeve sections 13a can be opened sufficiently wide to enable them to be placed transversely around the casing section B, the sleeve halvesthen being moved toward each other to interleave the hinge knuckles and allow the hinge pin 41 to be assembled in appropriate position through the hinge knuckles. It is only necessary for the hinge knuckles 40 and hinge pins 41 to be provided on the inner sleeve 13 of the sleeve structure. The outer sleeve 14, which has the bead portions 15, is made in two sections 14a and is welded to the inner sleeve and need not have any hinges formed thereon at all. The outer sleeve sections 14a terminate circumferentially at locations adjacent the outwardly directed hinge knuckles 40 of the inner sleeve 13, to avoid interference to the opening and closing movement of the sleeve 10 around the casing section.

inasmuch as the bead 15 need only contain the relatively small diameter wire bases 23 of the spring elements 2.2, which bases are essentially straight, although they may curve -slightly to conform to the curvature of the pumped down and out of the casing string, such cement l slurry passing upwardly through the annulus` around the casing string where it will eventually set and harden. The absence of the mud cake C on the wallof the well bore will insure a good cement bond with the formation and preclude subsequent leakage through the cement annulus formed around the -casing string. Y

For the purpose of facilitating mounting of the scratcher device A on the casing string, it is preferred that the scratcher device be made in sections that will enable the apparatus to be moved transversely or laterally onto and around the casing B. Thus, each sleeve structure 10 is made in two parts, rather than as a single circurnferentially continuous annulus. Each half 13a of the inner sleeve 13 is formed `with hinge knuckles d@ at its ends, the knuckles on onesleeve section 13a interleaving with the hinge knuckles of the other sleeve section 13a. A suitable hinge pin 41 can. be inserted through the hinge knuckles 40 to completefthe circumferential continuity sleeves .13, 14the vbead 15 `need not be large and` need not extend laterally outward to any substantial degree, while still providing an inner groove 26 that is much larger in both longitudinal and transverse dimensions than the diameter of the wire base 23. The fact that the beads 15 need not project outwardly to any substantial extent allows the inner sleeve 13 to be made of substantial thickness and possess great strength. Despite the use of the thicker inner sleeve, the over-al1 maximum diameter of the sleeve structure 10 across its bead portion 15 is not greater than prior beaded structures, in which the inner portions of the spring elements 22 were in the form of coil springs. The stronger and sturdier inner sleeve 13 not only insures that the sleeve structure will not be deformed, or otherwise damaged, during operation of the apparatus, but it `also insures the provision of substantially stronger hinge knuckles 40 and enables stronger hinge pins 41 to be used, guarding against inadvertent disruption of the apparatus at its hinges.

The inventor claims:

1. In a wall scratcher: an annular structure having an apertured, outwardly directed bead formed therein; a plurality of spring elements arranged circumferentially around said structure,'each element including a pair of laterally outwardly projecting fingers extending through different bead apertures and an intermediate substantially straight linear portion disposed within said bead and 4merging into said fingers; said apertures being of a greater area than the area of said fingers to permit rotation of said spring elements in said bead; a portion of said bead adjacent each aperture being adapted to abut each finger while the intermediate portion attached to such finger engages said bead to prevent rotation of said element in the annular structure beyond a predetermined point, at which point the outer end of each finger extends at substantially its maximum distance laterally outward from said structure; and means engageable with said elements to prevent substantial movement of said elements inwardly of said structure.

2. In a wall scratcher: an annular structure having an apertured, outwardly`directed `bead formed therein; a plurality of spring elements arranged circumferentially around said structure, each element including a` pair of laterally outwardly projecting fingers extending through different bead apertures and an intermediate substantially straight linear portion disposedv within said bead and merging into said fingers; said apertures being of a greater area than the area of ysaid fingers to permit rotation of said spring elements in said bead; means engageable with said elements to prevent'substantial movement of said elements inwardly of said structure; a portion of said bead adjacent the lower end of each aperture being adapted to abut each finger while the intermediate portion at tached totsuchl finger engages said bead and engagea-ble means `to preventrotation of said element in the annular; structure beyond :a predetermined point, at which point the Vouter fend of each V.finger extends at substantially its maximum distance laterallyoutward from said structure. i 3. In a wall scratcher: an annularrstructure having an apertured, outwardly directed bead formed therein, each aperture extending from-the upper portion of said bead to the medial portion of 'said bead; a plurality :of spring elements arranged circumferentially around said structure, each element including apairrof laterally outwardly projecting fingersextending through different bead apertures and an intermediate substantially straight linear portion disposed within said bead and merging into said `fingers; said aperturesbeing of a greater areathan the areaof said fingers to permit rotation of .said spring elements in said bead; a portion of said bead adjacent the lower end of each aperture being adapted to abut each finger while the intermedia-te portion attached to such finger engages said bead to `prevent lrotation of said element in the annular structure beyond a predetermined point, at which point the outer Vend `of each finger extends at substantially its maximum distance laterally outward from said structure; and means engageable with said elements to prevent substantial-movement of said elements inwardly lof said structure.

4. -In a wall scratcher: an annular structure having an apertured, outwardly directed bead formed therein; a plurality-of spring elements arranged circumferentially around `said vstructure and including laterally outwardly projecting fingers extending through said apertures, said elements including substantially straight linear portions disposed within said bead and merging into said fingers; said apertures being of a greater area than the area of said fingers -to permitrotation Vof said spring elements in said bead; a -portion of said bead adjacent the lower end of each aperture being adapted to abut eachfinger while the straight portion attached to such finger engages said bead to prevent rotation of said element in the annular structure beyonda predetermined point, at which point the outer end of `each fingerV extends at substantially its maximum distance laterally outward from said structure; and means engageable withsaid elements to prevent substantial movement of said elements inwardly of said structure Y .Y

5. In a wallfscratcher: an annular structure having an apertured, outwardly directed l-beadf formed therein, each aperture vextendingfrom the upper portion of said bead to the medial portion of rsaidfbead; a plurality of spring 'elements arranged circumferentially Varound said structure and including laterally outwardly -projecting lingers extending through said apertures and substantially straight linear portions disposed within said beadv and merging-into said fingers; said apertures bein-g ofi a greater area `than the area-ot` said fingers lto permit rotation of said-spring elements in said bead; a portion of said bead adjacent the lower end of each aperture being adapted to abuteach finger while the straightportion attached to such finger engages said bead -to-iprevent rotation of said element in thefannular structure beyond a predetermined point, at which point the outer end of each finger extends at substantially its maximum` distance laterally outward from said structure; and means engageable with Vsaid-elements toy prevent substantial movement of saidelements inwardly of said structure. v it 6. In a wall scratcher: an annular structure having an internal groove therein and4 a plurality of apertures extending .through-said structure from its exterior into said v groove; a plurality of spring elements arranged circumferentially around said structure and including laterally outwardly projecting `fingers-extending through said apertures and substantially straight linear portions disposed twithinssaid` groove and merging into said fingers; said apertures being of a--greater area than the area of said fingers .to permit rotation of said spring i elements in said groove; a portion of said structure adjacent the lower end of each aperture being adapted to abut .each finger while the-straightzportion attached to such .ngerengages the wallof said ,groove to prevent `rotation :of said element in `the annular structure beyond a `predetermined point, at which point-the outer end of each finger extends ait substantially its maximum distance laterally outward from said structure;.and means engageable Withsaid elements to prevent substantial movement o f said elements inwardly of said structure.

7. in a wall scratcher.: a supporting structure having an internal groove and atplurality of apertures extending through said structure from .its exterior into said groove; a plurality of spring elements arranged along 'said structure and including laterally outwardly projecting fingers extending through said apertures and substantially straight linear portions disposed within said groove and merging into said fingers; `said apertures being of a Ygreater area than the area of said fingers to permit rotation of `said spring elements in said groove; a portion of .said structure adjacent one side of each aperture being adapted to abut each finger while the straight portion attached to such finger engages the wall of saidrgroove to prevent rotation of said element in the structure beyond a predetermined point, at which point the outer end of each nger extends at substantially its maximum distance laterally outward from said structure; and means engageable with said elements to prevent substantial movement of said elements inwardly of said structure.

8. In a wall scratcher: a supporting structure having an internal groove and a plurality of apertures extending through said structure from its exterior into said groove; a plurality of spring elements arranged along said structure, each element including a pair of laterally outwardly projecting fingers extending through different apertures and an intermediate substantially straight linear portion disposed within said groove and vmerging into-said fingers; said aperturesbeing of a greater area than the areal of said fingers to premit rotation of said spring-elements in said groove; means adapted to abut each springV element to prevent rotation of said element in the structure beyond a predetermined point, at which point the outer end of each finger extends at substantially its maximum distance laterally outwardfrorn said structure, said means comprising a portion of said structure adjacent said aperture which is engaged by a portion of each spring element while said straight portion engages the wall of said groove; and means engageable with said elements to prevent substantial movement of said elements inwardly of said structure.

9. In a wall scratcher: a supporting structure having an internal groove and a plurality of apertures extending through said structure from itsv exteriorinto said groove; each aperture extending from one side of said groove to the medial portion of said groove; a plurality ofV spring elements arrangedV along said structure and inclu-ding laterally outwardly projecting fingers extending through said apertures and substantially straight linear portions disposed within said groove and merging into said fingers; said aperturesrbeing of a greater area than the area of said fingers to permit'rotation of said spring elements in said groove; the portion of said structure medially of the groove and adjacent each aperture being adapted to abut each finger while the straight portion attachedto such finger engages the ywall of said groove to Yprevent rotation of said element in the structure beyond a predetermined point, at which point the outer end of each finger extends at substantially its maximum distance laterally outward from said structure; and means engageable with said elements to prevent substantial movement of said elements inwardly of said structure.

' 10. In a wall scratcher: an outer annular member having an apertured, Voutwardly directed-bead formed therein; a plurality of spring elements arranged circumferentially around said member, each element' including a" pair vof laterally outwardly projecting fingers extending through diferentbead4 apertures and an intermediate substantially straight linear portion disposed within said bead and merging into said fingers; said apertures being of a greater area than` the area of said fingers to permit rotation of said spring elements in said bead; means adapted to abut each spring element while said straight portion engages the' wall of said groove; and an inner annular member disposed within and secured to said outer annular member and arranged across said bead to prevent substantial movement of said elements inwardly of said outer member.

l1. In a wall scratcher: an outer supporting member having an inner groove therein and a plurality of apertures extending through said member from its exterior into said groove, each aperture extending from one side of said groove to the medial portion of said groove, a plurality of spring elements arranged along said member and including laterally outwardly projecting fingers extending through said apertures and substantially straight linear portions disposed within said groove and merging into said lingers; said apertures being of a greater area than the area of said fingers to permit rotation of said spring elements in said groove; a portion of said member adjacent the medial portion of said groove being adapted to abut each finger while the straight portion attached to such finger engages the wall of said groove to prevent rotation of said element in the outer member beyond a predetermined point, at which point the outer end of each finger extends at substantially its maximum distance laterally outward from said structure; and an inner member disposed within and secured to said outer member and arranged across said groove to prevent substantial movement of said element inwardly of said outer member.

l2. In a wall scratcher: an outer annular member having an apertured, outwardly directed bead formed therein; a plurality of spring elements arranged circumferentially around said member, each element including a pair of laterally outwardly projecting fingers extending through different bead apertures and an intermediate substantially straight linear portion disposed within said bead and merging into said fingers; said apertures being of a greater area than the area of said fingers to permit rotation of said spring elements in said bead; means adapted to abut each spring element to prevent rotation of said element in the outer member beyond a predetermined point, at which point the outer end of each finger extends at substantially its maximum distance laterally outward from said structure, said means comprising a portion of said bead adjacent said aperture which is engaged by a portion `of each spring element while the straight portion attached to such finger engages said bead; an inner annular member disposed within and secured to said outer annular member and arranged across said bead to prevent substantial movement of said elements inwardly of said outer member, said inner and outer annular members each comprising a plurality of sections; and hinge means detachably securing said inner member sections together.

13. In a wall scratcher: an annular structure having an apertured, Voutwardly directed bead formed therein; a plurality of spring elements arranged circumferentially around said structure, each element including a pair of laterally outwardly projecting fingers extending through different bead apertures and intermediate portions disposed within said bead; said apertures being of a greater area than the area of said fingers to permit rotation of said spring elements in said bead; means adapted to abut each spring element to prevent rotation of said element on the structure beyond a predetermined point, said means comprising a portion of the bead -adjacent said aperture which is engaged by a portion of each spring element; the fingersof each element having inner portions converging in an outward direction with respect to each other and outer portions diverging in an outward direction with respect to each other so as to overlap and contact the lingers of adjacent elements in a direction circumferentially around'said supporting structure; and means engageable with said elements to `prevent substantial movement of said elements inwardly of said supporting structure.

14. In a wall scratcher: a supporting structure having an internal groove and a plurality of apertures extending through said structure from its exterior into said groove; a plurality of spring elements arranged along said structure, each element including a pair of laterally outwardly projecting fingers extending through different apertures and an intermediate portion disposed within said groove; said apertures being of a greater area than the area of said tingers to permit rotation yof said spring elements in said groove; means adapted to abut each spring element to prevent rotation of said element on the supporting structure beyond a predetermined point, said means comprising a portion of the supporting structure adjacent said aperture which is engaged by a portion of each spring element; the fingers of each element having inner portions converging in an `outward direction with respect to each other and outer portions diverging in an outward direction with respect to each other so as to overlap and contact the fingers of adjacent elements in a direction along said supporting structure; and means engageable with said elements to prevent substantial movement of said elements inwardly of said supporting structure.

l5. In a wall scratcher: an outer annular member having an apertured, outwardly directed bead formed therein; a plurality of spring elements arranged circumferentially -around said member, each element including a pair of laterally outwardly projecting fingers extending through different bead apertures and an intermediate substantially straight linear portion disposed within said bead and merging into said fingers; each aperture extending from the upper portion of said bead to the medial portion of said bead; said apertures being of a greater area than the area of said fingers to permit rotation of said spring elements in said bead; a portion of said bead adjacent the lower end of each aperture being adapted to abut each finger to prevent rotation of said element in the annular member beyond a predetermined point; the fingers of each element having inner portions converging in an outward direction with respect to each other and outer portions diverging in an outward direction with respect to each other so as to overlap and contact the ngers of adjacent elements in a direction circumferentially around said outer member; and an inner annular member disposed within and secured to said outer annular member and arranged across said bead to prevent substantial movement of said elements inwardly of said outer member.

16. In a wall scratcher: a supporting structure having an internal groove and a plurality of apertures extending through said structure from its exterior into said groove; a plurality of spring elements arranged along said structure and including laterally outwardly projecting fingers extending through said apertures and substantially straight linear portions disposed lengthwise within said groove and merging into said fingers; said apertures being of a greater area -than the area of said fingers to permit rotation of said spring elements in said groove; means engageable with said elements to prevent substantial movement of said elements inwardly of said structure; a portion of said structure adjacent one side of each aperture being adapted to abut each finger while the straight portion attached to such finger simultaneously engages the wall of said groove and said engageable means to prevent rotation of said element in the structure beyond a predetermined point, Vat which point the outer end of each finger extends at substantially its maximum distance laterally outward from said structure.

t ;`l7. In afwallscrateher: an outer annulargmember havinga'n apertured, outwardlyrected bead formed therein; a .plurality of Vspring elements arranged eircumterentially around said member, yeaehl element ineludiuga Vpair of laterally outwardly projecting lingersV extending .through different bead. apertures and zanintermedi-'ate vsubstantially straight linear portion disposed lengthwise AWithin :said beadandmergiug into said 'ngers; saidapertureslneiugof a greater area than the area of said :lingers to permit :roi- Y tation of said spring' elements iin said bead; an ini-ler `annul'ar member disposed within and 4secured to lsaid outer annular member and arranged across said 'bead to prevent substantial movement ofV 'said elements'inwardly of 'said outer member; means adapted 'to abut Seach spring element to prevent v.rotation of :said element in the outer member beyond.a;predetermined.point, at which point the outer Aend ofreachugerextends atxsubstantiallyits maximum `-distance laterally outward from .said annular. member, said means comprisingaportion of said outer'mernber :adjacent said :aperture which is 'engaged Ybyra portion of each spring element while said straight portionfsimultaneously engages th'ewallxof saidgroove and vsaid inrler annular member.

Referencesitd ilthele of this patent UNITED STATES jrATENrs` 

